Wire Guage Sizes

I think Swifty has a point. (nothing to do with the code, but a point nonetheless)

Oftentimes in commercial and Industrial circuits are spec'd to be as large as #4 CU for a 20A branch circuit. This is for Voltage Drop. Except for RARE instances VD is not an issue for homeowners. I've never felt the need to switch conductor sizes in a house.

Wire Guage Sizes

Majorty of the Resdentail area i useally not really worry about the VD because majorty of the runs are about 100 feet or less [ 30 metres or less ]

but other hand in commercal/ industrial location it will be diffrent ballpark of game you have to deal with this. this will get pretty common that why i useally automatically expect the wire size useally bump up a size or two. due very long run esepcally this is true with luminaire circuits. [ parking lot is worst ]

that why i useally dont advise not too much in resdentail area but there are few spots have to watch out is spa circuit's and few other but each case are diffrent.